From mboxrd@z Thu Jan 1 00:00:00 1970 From: ludo@gnu.org (Ludovic =?utf-8?Q?Court=C3=A8s?=) Subject: Re: Rollback problems Date: Thu, 24 Jan 2013 21:52:59 +0100 Message-ID: <87bocel2vo.fsf@gnu.org> References: <201301232148.46744.andreas@enge.fr> <87mwvzsdzt.fsf@gnu.org> <201301240017.55013.andreas@enge.fr> <87mwvystku.fsf@gnu.org> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Return-path: Received: from eggs.gnu.org ([208.118.235.92]:40579) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1TyTnE-0008CZ-Qp for bug-guix@gnu.org; Thu, 24 Jan 2013 15:53:10 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1TyTnC-00056X-DP for bug-guix@gnu.org; Thu, 24 Jan 2013 15:53:04 -0500 Received: from mail2-relais-roc.national.inria.fr ([192.134.164.83]:31422) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1TyTnC-00056N-7A for bug-guix@gnu.org; Thu, 24 Jan 2013 15:53:02 -0500 In-Reply-To: <87mwvystku.fsf@gnu.org> ("Ludovic \=\?utf-8\?Q\?Court\=C3\=A8s\=22'\?\= \=\?utf-8\?Q\?s\?\= message of "Thu, 24 Jan 2013 12:34:25 +0100") List-Id: Bug reports for GNU Guix List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: bug-guix-bounces+gcggb-bug-guix=m.gmane.org@gnu.org Sender: bug-guix-bounces+gcggb-bug-guix=m.gmane.org@gnu.org To: Andreas Enge Cc: bug-guix@gnu.org Hello, So Andreas and I discussed this IRL=E2=80=93we happen to be in the same loc= al GGUUG[*]. Here=E2=80=99s a summary. Issues were: 1. Should generations from which we roll back be kept? 2. If not, should they be deleted directly after a successful roll-back, or just when a new diverging generation is built? 3. More generally, should the history of generations be linear, or should it be a DAG like Git commits? Regarding (3), it seems that a linear history not only simplifies the implementation, but also the user interface, while covering most practical use cases. Having agreed on linear history, it seems that (a) the current behavior is broken because roll-backs don=E2=80=99t actually follow the history, as illustrated previously, and (b) the generation from which we are rolling back must be deleted. Let me illustrate. Suppose these generations: A ------> B ------> C When doing a roll-back from C, one should obviously get back at B. At that point, C would still be available. Keeping it around means that users can easily switch back to C if B turned out to be less appropriate (this answers questions (1) and (2)). Once at B, installing or removing packages would delete C, thus allowing its generation number to be reused, and create a new generation C=E2=80=99 = with the same generation number as C: A ------> B ------> C=E2=80=99 At this point, switching back to C is no longer possible. Thoughts? I=E2=80=99ll implement that if there are no objections. Ludo=E2=80=99. [*] GNU Guix United User Group